Port plates for hydraulic reciprocating pumps and motors



Aug. 12, 1969 H s. BOTTOMS PORT PLATES FOR HYDRAULIC RECIPROCATING PUMPSAND MOTORS Filed Sept. 15, 1967 2 Sheets-Sheet 1 A g 1969 H. s. BOTTOMS3,460,433

- PORT PLATES FOR HYDRAULIC RECIPROGATING PUMPS AND MOTORS Filed Sept.15, 1967 2 Sheets-Sheet 2 FIG. 2

United States Patent 3,460,483 PORT PLATES FOR HYDRAULIC RECIPROCAT- INGPUMPS AND MOTORS Harry Simister Bottoms, Solihull, England, assignor toJoseph Lucas (Industries) Limited, Birmingham, England, a Britishcompany Filed Sept. 15, 1967, Ser. No. 667,902 Int. Cl. F04d 1/ 00 US.Cl. 103--162 5 Claims ABSTRACT OF THE DISCLOSURE In an hydraulic swashplate type pump or motor there is a port plate having straight insertsdisposed in straight grooves in its surface, said inserts defining aclosed regular and symmetrically disposed figure about the ports in theport plate.

This invention is applicable to hydraulic pumps and motors of the kindcomprising a body having an inlet and an outlet for liquid, a rotormounted in the body containing a plurality of reciprocatory pistons inrespective bores therein, means for reciprocating the pistons as therotor rotates, and a port plate disposed between the rotor and the partof the body through which the inlet and outlet extend. Such a pump ormotor will be referred to as being of the kind specified.

The face of the port plate against which the rotor engages has beenprovided with one or more inserts of material such as carbon to providegood bearing surfaces and also to sustain the loads applied thereto andit has been proposed to form these inserts as rings. However, somematerials such as, for example, carbon, are so brittle that it has beenfound diflicult to machine relatively large rings without crackingoccurring.

The object of this invention is to provide a port plate for a pump ormotor of the kind specified in which this problem is overcome orreduced.

The present invention resides in the provision of a port plate for apump or motor of the kind specified having, in its face intended to bedisposed adjacent to the rotor, a plurality of straight slots containingstraight inserts respectively, the inserts defining a closed regularfigure surrounding the ports in the plate, and being symmetrical aboutthe axis of rotation of the rotor.

The invention will now be described with reference to the accompanyingdrawings in which:

FIGURE 1 is a cross-sectional side elevation view of a pump or motorincorporating the present invention, and

FIGURE 2 is an end elevation view of a port plate for use in the pump ormotor of FIGURE 1.

The pump or motor to which this invention is applied comprises a body inwhich is rotatably mounted a rotor 11 having a plurality of bores 12containing respective reciprocatory pistons 13. The body 10 has at oneend, an inlet 14 and an outlet 15 for liquid, and at the opposite end ofthe rotor 11 is disposed an inclined swashplate 16, the angularity ofwhich can be varied, and against which the pistons 13 are urged byrespective springs 17 in the bores 12 in the rotor 11. Between the endof the rotor 11 remote from the swash plate 16 and the end of the body10 in which the inlet 14 and outlet 15 are formed, is disposed a portplate 18 which is held against angular movement relatively to the body,and in which are formed two kidney shaped ports 19, 20 communicatingwith the inlet 14 and with the outlet 15 respectively, and affordingcommunication between the inlet 14 and the outlet 15 and the bores 12 inthe rotor 11 in turn as the rotor rotates within the body 10.

3,460,483 Patented Aug. 12, 1969 The port plate 18 has its kidney shapedports 19, 20 disposed symmetrically about the axis of rotation of therotor 11. The face of the port plate 18 which is illustrated in FIGURE2, is that which is intended to be disposed adjacent to the rotor endface. To provide bearing surfaces against which the rotor end faceengages there are a plurality of inserts formed, for example, from amaterial such as vitreous carbon. There is an inner ring like insert 21inside the inner margins of the ports 19, 20 and mounted in an annulargroove. Surrounding the ports 19, 20 are a plurality of further inserts22, in the form of straight strips of carbon disposed in appropriatelyshaped slots 23 respectively, formed in the face of the port plate 18,the inserts 22 defining in the example illustrated, a closed regularhexagonal figure. The slot lengths exceed those of the strip inserts 22and, as illustrated, the inserts 22 are arranged to butt, one againstthe next, one end of each being inclined for this purpose. The directionof rotation of the rotor relatively to the port plate 18 is indicated bythe arrow 24, this relative rotation tending to hold the inserts 22 inclose contact with one another at the appropriate end thereof.

The annular groove for the insert 21 and the straight slots 23 for thestraight inserts 22 are conveniently machined. The straight inserts 22are preferably disposed in grooves 23 which, as illustrated, are longerthan the inserts 22 themselves. These grooves 23 may be formed bymilling or other machining operations.

Between the ends of the ports 19, 20 and extending near radially arefurther straight inserts 25 in respective slots 26. These furtherinserts 25 extend between the outer surface of the ring 21 and theinwardly presented surfaces of the inserts 22.

All the inserts 21, 22 and 25 extend above the adjacent surface of theport plate 18 itself.

In an alternative construction, however, the surfaces of the inserts areonly slightly proud of the port plate surface and the inserts 25 may beomitted in this form of the invention. An example of the projection ofthe inserts with respect to the surface of the port plate is 0.002 inch.

It is to be understood that the inserts 22 can define any regular closedfigure enclosing the ports 19, 20 in the port plate 18, but this figureshould be symmetrical about the axis of rotation of the rotor relativelyto the port plate 18.

It has been found that the manufacture of straight strips of materialssuch as carbon, which are brittle, can be more readily accomplishedwithout cracking than the manufacture of relatively large size rings,and the invention therefore offers substantial manufacturing advantage.

The width of the inserts 22 must be calculated to correspond with thedesired pressure balance between the rotor and valve plate.

Having thus described my invention what I claim as new and desire tosecure by Letters Patent is:

1. A port plate for an hydraulic machine having two kidney shapedsymmetrically arranged ports, and having, in its face, a plurality ofstraight slots containing straight inserts respectively, the insertsdefining a closed regular figure surrounding the ports in the plate, andbeing symmetrical about the centre of the plate, the inserts beingformed from vitreous carbon.

2. A port plate as claimed in claim 1 in which a further insert of ringlike form is disposed inside the inner margins of the ports.

3. A port plate as claimed in claim 2 in which there are furtherstraight inserts in respective slots disposed between the ends of theports and extending generally radially between the external surface ofthe ring-like insert and the inwardly presented surfaces of the straightinserts.

4. A port plate as claimed in claim 3 in Which the inserts extend abovethe adjacent surface of the port plate.

5. An hydraulic machine comprising a body having an inlet and an outletfor liquid, a rotor mounted Within the body, a plurality of pistonsdisposed within respective bores in the rotor, means for reciprocatingthe pistons as the rotor rotates, and a port plate disposed between therotor and that part of the body through which the inlet and outletextend, the port plate having two kidney shaped symmetrically arrangedports and having in its face, a plurality of straight slots containingstraight inserts respectively, the inserts defining a closed regularfigure surrounding the ports in the plate, and being sym- ReferencesCited FOREIGN PATENTS 8 /1965 Canada.

ROBERT M. WALKER, Primary Examiner metrical about the centre of theplate, the inserts being 15 0' 9 formed from vitreous carbon.

U.S. Cl. X.R.

